The sweet potato (Ipomoea batatas), often incorrectly called a yam in the United States, is a cropplant whose large, starchy, sweet tasting tuberous roots are an important root vegetable. The young leaves and shoots are sometimes eaten as greens. The sweet potato is only distantly related to the potato (Solanum tuberosum). They are even more distantly related to the true yam (Dioscorea species).

The genusIpomoea that contains the sweet potato also includes several garden flowers called morning glories, though that term is not usually extended to Ipomoea batatas. Some cultivars of Ipomoea batatas are grown as houseplants.

The plant is a herbaceousperennialvine, bearing alternate heart-shaped or palmately lobed leaves and medium-sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose color ranges between red, purple, brown and white. Its flesh ranges between white, yellow, orange, and purple.

Origin and distribution

Sweet potatoes are native to the tropical parts of the Americas, and were domesticated there at least 5000 years ago. [1][2] They spread very early throughout the region, including the Caribbean. They were also known before western exploration in Polynesia. How exactly they arrived there is the subject of a fierce debate which involves archaeological, linguistic and geneticevidence.

Sweet potatoes are now cultivated throughout tropical and warm temperate regions wherever there is sufficient water to support their growth.

According to 2004 FAO statistics world production is 127,000,000 tons [3]. The majority comes from China with a production of 105,000,000 tonnes from 49,000 km². About half of the Chinese crop is used for livestock feed [4].

Per-capita production is greatest in countries where sweet potatoes are a staple of human consumption, led by the Solomon Islands at 160 kg per person per year and Burundi at 130 kg.

North Carolina is the leading U.S. state in sweet potato production. Currently, North Carolina provides 40% of the annual U.S. production of sweet potatoes.

Mississippi is also a major sweet potato producing state, where they are grown on approximately 8,200 acres. Mississippi sweet potatoes contribute $19 million dollars to the economy of the state and around 150 Mississippi farmers presently grow sweet potatoes. Mississippi's top five sweet potato producing counties are Calhoun, Chickasaw, Pontotoc, Yalobusha and Panola. The National Sweet Potato Festival is held annually the entire first week in November in Vardaman, MS, which proclaims itself as "The Sweet Potato Capitol".

The town of Benton, Kentucky, celebrates the sweet potato annually with its Tater Day Festival on the first Monday of April.

Cultivation

The plant does not tolerate frost. It grows best at an average temperature of 24 °C (75 °F). Depending on the cultivar and conditions, tuberous roots mature in 2 to 9 months. With care, early-maturing cultivars can be grown as an annual summer crop in temperate areas, such as the northern USA. Sweet potatoes rarely flower when the daylight is longer than 11 hours, as is normal outside of the tropics. They are mostly propagated by stem or root cuttings or by adventitious roots called "slips" that grow out from the tuberous roots during storage. True seeds are used for breeding only.

Under optimal conditions of 85 to 90 % relative humidity at 13 to 16 °C (55 to 61 °F), sweet potatoes can keep for six months. Colder temperatures injure the roots.

Sweet potatoes are often considered a small farmer's crop. They grow well in many farming conditions and have few natural enemies; pesticides are rarely needed. They can be grown in poor soils with little fertilizer. Because they are sown by vine cuttings rather than seeds, sweet potatoes are relatively easy to plant. Because the rapidly growing vines shade out weeds, little weeding is needed, and farmers can devote time to other crops. In the tropics the crop can be maintained in the ground and harvested as needed for market or home consumption. In temperate regions sweet potatoes are most often grown on larger farms and are harvested before frosts set in.(CGIAR)

China is the largest grower of sweet potatoes; providing about 80% of the world's supply, 130 million tons were produced in one year (in 1990; about half that of common potatoes). Historically, most of China's sweet potatoes were grown for human consumption, but now most (60%) are grown to feed pigs. The rest are grown for human food and for other products. Some are grown for export, mainly to Japan. China grows 100 varieties of sweet potato.(JRT)

Sweet potatoes very early became popular in the islands of the Pacific, from Japan to Polynesia. One reason is that they were favored as an emergency crop that could be relied on if other crops failed due to typhoon flooding and the like. They are featured in many favorite dishes in Japan, Taiwan, the Philippines , and other island nations. Indonesia, Vietnam, India, and some other Asian countries are also large sweet potato growers. Uganda (the third largest grower after Indonesia), Rwanda, and some other African countries also grow a large crop which is an important part of their peoples' diets. North and South America, the original home of the sweet potato, together grow less than three percent of the world's supply. Europe has only a very small sweet potato production, mostly in Portugal.(JRT)(FAO)

Sweet potatoes were an important part of the diet in the United States for most of its history, especially in the Southeast. In recent years however they have become less popular. The average per capita consumption of sweet potatoes in the United States is only about 1.5-2 kg (4 lbs) per year, down from 13 kg (31 lb) in 1920. Southerner Kent Wrench writes: "The SweetPotato became associated with hard times in the minds of our ancestors and when they became affluent enough to change their menu, the potato was served less often."(NCSPC)

Diseases

Uses

The roots are most frequently boiled, fried, or baked. They can also be processed to make starch and a partial flour substitute. Industrial uses include the production of starch and industrial alcohol.

Culinary Uses

Although the leaves and shoots are also edible, the starchy tuberous roots are by far the most important product. In some tropical areas, they are a staple food-crop. Besides starch, they are rich in dietary fiber, vitamin A, vitamin C, and vitamin B6. All cultivars are more-or-less sweet-flavored. Despite the name "sweet", it is actually a good food for diabetics as preliminary studies on animals have revealed that it helps to stabilize blood sugar levels and lowered insulin resistance.<ref>Sweet potatoes</ref>

In 1992, the Center for Science in the Public Interest compared the nutritional value of sweet potatoes to other vegetables. Considering fiber content, complex carbohydrates, protein, vitamins A and C, iron, and calcium, the sweet potato ranked highest in nutritional value. According to these criteria, sweet potatoes earned 184 points, 100 points over the next on the list, the common potato.(NCSPC)

Sweet potato varieties with dark orange flesh have more Vitamin A than those with light colored flesh and their increased cultivation is being encouraged in Africa where Vitamin A deficiency is a serious health problem.

Candied sweet potatoes are a side dish consisting mainly of sweet potatoes prepared with sugar, marshmallows, maple syrup, molasses, or other sweet ingredients. Often served on American Thanksgiving, it represents traditional American cooking and indigenous food. Some Americans, including television personality Oprah Winfrey, are advocating increased consumption of sweet potatoes both for their health benefits and because of their importance in traditional Southern cuisine.

Baked sweet potatoes are sometimes offered in restaurants as an alternative to baked potatoes. They are often topped with brown sugar and butter.

Boiled sweet potato leaves are a common side dish in Taiwanese cuisine, often boiled with garlic and vegetable oil and dashed with salt before serving. They are commonly found at biàndāng restaurants, as well as dishes featuring the sweet potato root.

Steamed/Boiled chunks, for a simple and healthy snack, chunks of sweet potato may be boiled in water or cooked in the microwave.

Sweet potato chips, they can be sliced, fried, and eaten just like potato chips or french fries] like at the Taiwan chain of T.K.K. Fried Chicken International restaurants.

Non-Culinary Uses

In South America, the juice of red sweet potatoes is combined with lime juice to make a dye for cloth. By varying the proportions of the juices, every shade from pink to purple to black can be obtained. (Verrill p. 47)

Ethnomedical Uses

Names

The moist-fleshed, orange cultivars of sweet potato are often referred to as “yams” in the United States. One explanation of this confusion is that Africans brought to America took to calling American sweet potatoes Nyamis, perhaps from the Fulani word nyami (to eat) or the Twi word anyinam, which refers to a true yam. The true yam, which is native to Africa and Asia, can grow up to 2 m (6 ft) in length (sometimes with knuckle-like ends) and has a scaly skin, a pinkish white center, and a thick, almost oily feel to the tongue.

Later on many farmers and stores began marketing American-grown sweet potatoes as yams; the name stuck. In more recent times there has been an effort to stop the use of “yam” for sweet potatoes, but this has only been partially successful. USDA branding regulations require the word “yam” to be accompanied by the words “sweet potato” when referring to these moister sweet potatoes.

Starchy, white-fleshed types are sometimes called batatas or boniatos, from generic Spanish terms for all types of sweet potato.

Substratum names used in local varieties of English include Kūmara (from Māori), as it was the staple food of the native Māori diet, in the UK and Australasia (although "sweet potato" is more common in Australia, at least in Victoria) (the term is also used in indigenous languages of Melanesia, as well as "peteita"), and camote (from Nahuatlcamohtli via Spanish) in the southwestern United States.

In [[Hawaii|HawaiTemplate:Okinai]] substratum names are used for the yellow Japanese variety and the purple Okinawan variety, both of which are commonly available in the marketplace. The local Japanese names are widely recognized, with Satsumaimo “Satsuma potato” used by recent Japanese immigrant families and yamaimo (“mountain potato”) by other groups. (Technically, yamaimo is the proper name in Japanese of the native yam; however, as in English, it is often used to refer to the sweet potato.) However, naming often depends on personal ancestry, with e.g. SāmoanTemplate:Okinaumala among Sāmoans, Tagalogkamote among Filipinos, and HawaiianTemplate:Okinauala among Native Hawaiians. The orange-fleshed variety common in the mainland US and sold alongside the Japanese and Okinawan cultivars is locally called “sweet potato” or “yam”. The purple Okinawan sweet potato is sometimes confused with the purple yam called ube.

Varieties

There are seven major varieties of sweet potatoes: Jersey, Kotobuki (Japanese), Okinawan (Purple), Papa Doc, Beauregard, Garnet, and Jewel. The last three varieties are regionally called "yams" in the United States.

A unique variety of sweet potato grown in New Zealand, originally grown by the indigenous Maori, is the Kumara, a red/purple variety with a unique flavor due to its isolation from other varieties.

Sweetpotato DiagNotes is a free comprehensive tool for sweetpotato management, providing information across the disciplines of plant pathology, crop nutrition, entomology and pest management, all integrated in a single expert system.

Mississippi Sweet Potato Growers Association website highlights the efforts of Wardell Sanders and his pursuits in Mound Bayou, Mississippi. The SPGA serves to provide a lasting agri-economy, strengthen the area farming communities, heighten Mississippi Delta pride, and to include Delta youth in all phases of its operations.